Microstructured silver surfaces produced by freeze casting for enhanced phase change heat transfer

[摘要] Microporous silver surface layers were formed on copper substrates by means of a modified freeze casting method. The structure of such layers is the result of the templating action of the ice crystals and layers were found to contain a hierarchical porous structure. Three different pore morphologies were present in the microstructure with pore sizes ranging from approximately 0.5 to 200 μm. The application of these surface structures was found to considerably enhance the heat flux during the nucleate phase of pool boiling, with heat fluxes up to five times higher from a microporous surface compared to a bare copper substrate. Bubble formation and departure was found to be significantly different on the two types of surfaces, with smaller bubbles formed with a high density on the microporous surface. The enhancement in heat flux by these structures is most likely due to the combined effect of an increased surface area with high thermal conductivity, an increase in nucleation sites for bubble formation as well as effective wicking from micropores to sustain bubble growth and departure.

[发布机构] School of Engineering and Computer Science, Victoria University of Wellington, Wellington, New Zealand^1

[效力级别] 能源学

[关键词] Bare copper substrate;Copper substrates;Freeze casting methods;Hierarchical porous structures;High thermal conductivity;Micro-porous surfaces;Nucleation sites;Phase change heat transfer